JPH10318028A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly release the residual pressure of a pressure accumulating means by repeating a switching operation for the solenoid valve of an injector at a cycle shorter than a period for injecting fuel. SOLUTION: A feed pump 18 driven by engine power sucks fuel stored in a tank 15 and supplies fuel into the pressure room 13 of a pressure pump 10. The fuel in the pressure room 13 is pressurized by a plunger 11 and supplied to a common rail 23 and then the fuel is pressure-accumulated. The pressure of the common rail 23 is applied to an injector 26, electricity is conducted to a solenoid valve 59 to be excited and then fuel injection is carried out. In this fuel injection device, when a key switch is changed to be OFF, the solenoid coil 61 of the injector 26 is turned ON/OFF bit by bit by an electronic controller 30 at a short cycle and a time interval where fuel injection is not performed. Thus, back leakage is performed by the injector 26 and a pressure is reduced in the common rail 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device, and more particularly to a fuel injection device in which fuel pressure accumulated by an accumulator is applied to an injector having an electromagnetic valve, and fuel is injected by switching the electromagnetic valve. It relates to an injection device.

[0002]

2. Description of the Related Art As a fuel injection device for a diesel engine, a plunger is pushed up by a cam at every injection, and the engine speed is fed back to a control rack via a camshaft and a mechanical governor. There has been proposed a pressure-accumulation type fuel injection device instead of the Bosch type fuel injection pump which controls the supply amount of fuel injected each time.

[0003] A pressure accumulating type fuel injection device pressurizes fuel by a pressurizing pump, accumulates fuel pressurized on a common rail, for example, and switches a solenoid valve incorporated in an injector to make a hydraulic cylinder. The pressing force of the piston inside the cylinder is released, the nozzle needle is lifted to inject fuel, fuel pressure is applied again to the piston in the hydraulic cylinder at a predetermined timing, and the nozzle needle is pressed against the valve seat to pressurize the fuel. Injection is stopped.

[0004]

In such a pressure accumulating type fuel injection device, after the engine is stopped, the fuel pressure remains on the common rail constituting the pressure accumulating means as a residual pressure. If such a residual pressure is left as it is, there is a possibility that a safety problem may occur during maintenance.

[0005] The fuel pressure of the pressure accumulating means composed of a common rail must be adjusted in accordance with the combustion state required in accordance with the engine speed and the accelerator opening. In order to increase the pressure in the common rail, the pressurizing pump may be driven, but there has been no means for rapidly reducing the pressure in the common rail.

The present invention has been made in view of such a problem, and it is possible to quickly release the residual pressure of the pressure accumulating means when the engine is stopped and to arbitrarily reduce the pressure in the pressure accumulating means. It is an object to provide a simple fuel injection device.

[0007]

According to a first aspect of the present invention, there is provided a fuel injection system in which fuel pressure accumulated by an accumulator is applied to an injector having an electromagnetic valve, and fuel is injected by switching the electromagnetic valve. The present invention relates to a fuel injection device, characterized in that there is provided a means for repeatedly performing a switching operation of the solenoid valve of the injector in a cycle shorter than a period during which fuel is injected in response to an engine stop signal.

According to such a device, when the switching operation of the solenoid valve of the injector is repeatedly performed in a cycle shorter than the period during which fuel is injected in response to the engine stop signal,
The fuel is not injected, and the residual pressure of the accumulator is released by the injector.

According to a second aspect of the present invention, there is provided a fuel injection device in which fuel pressure accumulated by an accumulator is applied to an injector having an electromagnetic valve, and fuel is injected by switching the electromagnetic valve. A means for switching the solenoid valve of the injector at a period shorter than a period during which fuel is injected during the timing of performing the fuel injection.

Therefore, according to such an apparatus, the switching operation of the solenoid valve of the injector is performed at a shorter period than the period during which the fuel is injected during the timing of the fuel injection, so that the fuel is not injected and the fuel is injected. It is possible to quickly reduce the pressure of the pressure accumulating means.

[0011]

FIG. 1 shows an overall configuration of a fuel injection device having a fuel injector according to an embodiment of the present invention. This fuel injection device is used to pressurize fuel. A pressurizing pump 10 is provided. The pressurizing pump 10 includes a plunger 11, and the plunger 11 is pushed up by a cam 12 attached to a camshaft. Fuel in a pressurizing chamber 13 in a space above the plunger 11 is pressurized. Become so.

The fuel in the fuel tank 15 is stored in a segmenter 16.
The pressure is suctioned by a feed pump 18 through a filter 17 and supplied to a pressurizing chamber 13 above the plunger 11 of the pressurizing pump 10 through a fuel filter 19 provided on the discharge side of the feed pump 18. It has become so. The pressurizing chamber 13 leaks fuel to the tank 15 via the one-way valve 20.

The discharge side of the pressurizing chamber 13 is connected via a one-way valve 22 to a common rail 23 constituting a pressure accumulating chamber. A one-way valve 24 is attached to the common rail 23. The one-way valve 24 forms a pressure limiter, and opens when the pressure of the common rail 23 exceeds a set pressure to return fuel to the tank 15. The common rail 23 is connected to an injector 26 via a flow limiter 25. The flow limiter 25 performs a shut-off operation when the flow rate of the fuel flowing to the injector 26 abnormally increases, thereby preventing abnormal injection.

An electronic control unit 30 including a computer is provided to control the entire fuel injection system. The electronic control unit 30 is connected to a pressure sensor 31 that detects the pressure in the common rail 23. A pump control valve 32 is connected between the pressurizing chamber 13 of the pressurizing pump 10 and the one-way valve 20 on the leak side, and its electromagnetic coil 33 is controlled by the electronic control unit 30. ing.

The electronic control unit 30 is provided with an accelerator sensor 35 for detecting an amount of depression of an accelerator pedal, an engine rotation sensor 36 for detecting an engine speed, a cylinder discriminating sensor 37 provided in the engine, and a pump. The cylinder discrimination sensors 38 are respectively connected.

Next, the structure of the injector 26 connected to the common rail 23 via the flow limiter 25 will be described. As shown in FIGS. 1, 2 and 3, a nozzle body 40 is provided at the tip end of the injector 26. Is installed. The nozzle body 40 is the nozzle needle 4
The nozzle needle 41 is slidably held.
Is pressed against the valve seat 42 to control the injection of fuel from the injection port 43. Further, a fuel reservoir 44 is provided in the nozzle body 40, and the fuel pressure stored in the common rail 23 is constantly applied to the fuel reservoir 44 via a fuel passage 45.

The nozzle needle 41 has a push rod 48
Is pressed downward. The push rod 48 is pressed downward by a pressing spring 49, and the upper end of the push rod 48 is
Is pressed. The piston 50 is slidably supported in a hydraulic cylinder 51 provided on the body of the injector 26, and the hydraulic cylinder 5
An orifice 52 having a throttle hole formed in the center thereof is disposed so as to close the inlet side of the nozzle 1.

The orifice 52 will be described in more detail. The orifice 52 is disposed at the inlet of a hydraulic cylinder 51 provided in the nozzle body so as to slidably hold the piston 50. The orifice 52 has a small hole 53 at the center thereof. The upper edge of the small hole 53 is chamfered to form an inclined surface.

Another fuel passage 62 is formed in the injector 26 so that the fuel pressure stored in the common rail 23 is applied to the hydraulic cylinder 51 via the flow limiter 25. I have. Another orifice 54 is attached to a part of the fuel passage 62 in the middle.

A solenoid valve 59 shown in FIGS. 1 to 3 is incorporated in the upper part of the injector 26. The solenoid valve 59 is pressed downward by a compression coil spring 60 and is urged upward by a solenoid coil 61. And the solenoid coil 61
2A, the fuel passage 6 is not energized as shown in FIG. 2A.
5 and the hydraulic cylinder 51 are shut off. The fuel passage 65 communicates with a port 66 for releasing fuel.

Next, the operation of fuel injection by the system shown in FIG. 1 will be described. The feed pump 18 and the pressurizing pump 10 are driven by a part of the output of the engine. The feed pump 18 sucks the fuel in the tank 15 through the segmenter 16 and the filter 17 and
The fuel is filled into the pressurizing chamber 13 of the pressurizing pump 10 through the pump.

The fuel in the pressurizing chamber 13 is pressurized by the plunger 11 pushed up by the cam 12, and is supplied to the common rail 23 through the one-way valve 22, and the fuel is accumulated by the common rail 23. Here, at the time of pressurization by the cam 12 of the pressurizing pump 10, the pump control valve 32 is controlled to be opened and closed by an electromagnetic coil 33. The time during which the pump control valve 32 is closed is appropriately calculated in accordance with the deviation, and control is performed so as to always reach the target pressure.

This operation will be described in more detail. The control valve 32 provided in the pressurizing pump 10 is
The pump control valve 3
When the plunger 11 is pushed up when the plunger 11 is closed, the fuel is pressurized, and when the plunger 11 is pushed up when the control valve 32 is opened, the fuel is supplied to the control valve 32 and the one The pressure is returned to the tank 15 through the directional valve 20, and the pressure is released by the control valve 32. The pressurizing pump 10 turns on and off the control valve 32 to change the discharge amount, and is feedback-controlled so that the signal of the pressure sensor 31 of the common rail 23 becomes the target value given to the computer of the electronic control unit 30. It has become.

When the feedback control of the pressure in the common rail 23 by the electronic control device 30 as described above is not performed correctly due to some abnormality, and the pressure in the common rail 23 exceeds the set pressure of the one-way valve 24, The one-way valve 24 constituting the pressure limiter is opened, and the fuel pressure escapes to the tank 15 side.

In this way, a constant pressure is accumulated in the common rail 23, and this pressure is applied to the injector 26 via the flow limiter 25.

FIG. 2A shows the injector 26 at the time of no injection, and the solenoid coil 61 is in a non-excited state.
Accordingly, the solenoid valve 59 is pressed downward by the compression coil spring 60, and its tip is connected to the fuel passage 65 and the hydraulic cylinder 5
1 and the upper space. Therefore port 66
Is in a shut-off state, and the fuel pressure of the common rail 23 is
Acting on the upper surface of the piston 50 inside.

The fuel pressure of the common rail 23 simultaneously acts on the nozzle needle 41 through the fuel passage 45 and the fuel sump 44.

The force acting downward at this time is the sum of the downward force received by the piston 50 of the hydraulic cylinder 51 due to the fuel pressure and the force of the pressing spring 49 pressing the push rod 48 downward. On the other hand, the upward force is the force that the nozzle needle 41 receives so as to act upward by the fuel pressure at the fuel reservoir 44.

Here, the diameter of the piston 50 of the hydraulic cylinder 51 is much larger than the diameter of the sliding seal portion of the nozzle needle 41, and the downward force applied by the pressing spring 49 is much larger. Therefore, the front end portion of the nozzle needle 41 is pressed against the valve seat 42, and the nozzle needle 41 blocks fuel at the valve seat 42, so that no injection is performed.

The electronic control unit 30 detects the amount of depression of the accelerator pedal by an accelerator sensor 35,
The rotation speed of the engine is detected by the rotation detection sensor 36. Further, an optimum injection time and injection timing are calculated based on other information as needed. Then, the solenoid coil 61 is excited at a predetermined timing.

Then, the solenoid valve 59 is connected to the solenoid coil 61.
2B, the solenoid valve 5
9 lifts upward. Therefore, the solenoid valve 59 is separated from the valve seat, and the space above the hydraulic cylinder 51 is communicated with the port 66 via the fuel passage 65. Therefore, the fuel pressure that has pressed the piston 50 of the hydraulic cylinder 51 is reduced to the small hole 53 of the orifice 52 of the hydraulic cylinder 51.
Leakage occurs through the fuel passage 65 and the port 66. Therefore, the force of pressing the piston 50 of the hydraulic cylinder 51 downward by the fuel pressure is released.

Therefore, the nozzle needle 41 is moved to the fuel sump 44.
The pressing force of the pressing spring 49 overcomes the pressing force by the fuel pressure applied to the nozzle needle 41, the nozzle needle 41 is lifted upward, and the tip side portion of the nozzle needle 41 is separated from the valve seat 42. Therefore, fuel is injected through the injection port 43.

When releasing the fuel pressure acting on the upper part of the piston 50 of the hydraulic cylinder 51, the small hole 5 of the orifice 52 arranged at the inlet of the hydraulic cylinder 51 is released.
Since 3 is a throttle, the fuel pressure is released slowly. Therefore, the rising speed of the nozzle needle 41 with respect to the valve seat 42 is buffered.

Thereafter, when the excitation of the solenoid coil 61 is released again as shown in FIG.
The electromagnetic valve 59 is moved downward by this, and this electromagnetic valve 59
Cuts off between the fuel passage 65 and the inlet of the hydraulic cylinder 51. Further, the fuel pressure is applied to the upper surface of the piston 50 of the hydraulic cylinder 51 via the fuel passage 62 and the orifice 54, and strongly presses the nozzle needle 41 downward as shown in FIG. 2A. Then, the nozzle needle 41 is pressed against the valve seat 42 to shut off the fuel, and the fuel injection is stopped. The seating operation of the nozzle needle 41 at this time is buffered by the orifice 54.

As shown in FIG. 4, the fuel pressure required for the common rail 23 of the fuel injection device which injects fuel in this manner greatly fluctuates according to the engine speed and the engine output torque. . This is because the required combustion state changes according to the engine speed and the output torque, and it is necessary to change the fuel pressure applied to the injector 26 accordingly.
This makes it possible to always achieve optimal combustion.

In general, when increasing the pressure of the common rail 23, the control valve 32 is closed and the pressurizing pump 10 is driven to rotate to fill the common rail 23 with fuel. On the other hand, when depressurizing the fuel in the common rail 23, the solenoid valve 59 is opened for a period shorter than the fuel injection period of the injector 26, and the injector 26 is opened.
The pressure reduction operation is performed using the back leak.

As shown in FIG. 5, the fuel injection amount changes in accordance with the time for which the solenoid coil 61 for exciting the solenoid valve 59 of the injector 26 is energized. Here, when shorter than a predetermined time to energize the solenoid coil 61 time T _1, becomes the electromagnetic valve 59 is closed so before the nozzle needle 41 is lifted sufficiently, which fuel injection is not performed by. That is, the solenoid coil 61
Excitation time is less space than T ₁ is made to non-injection region of.

Even in the non-injection region, since the solenoid valve 61 is lifted by the solenoid coil 61, the fuel pressure supplied to the hydraulic cylinder 51 through the fuel passage 62 is reduced from the hydraulic cylinder 51 to the orifice 52 and the fuel passage. 65, leak through port 66. Therefore, the fuel in the common rail 23 is depressurized by such a leak.

In the fuel injection device according to the present embodiment, the pressure in the common rail 23 is reduced by utilizing such a back leak of the injector 26.
As shown in FIG. 6, normal fuel injection is performed once every two revolutions of the crankshaft. That is, the solenoid coil 61 is excited once every 720 ° in crank angle, and the solenoid valve 59 is opened to perform fuel injection. For other periods, there is no need to inject fuel.

Therefore, as shown by the dotted line in FIG. 6, the solenoid coil 61 is provided with a very short timing between the period of performing the fuel injection and the period of performing the next fuel injection.
To excite. That energizing the solenoid coil 61 for a short time than time T ₁ shown in FIG. Even if the solenoid coil 61 is excited for such a short time, the injector 26 does not inject fuel because of the non-injection region as described above. However, such excitation of the solenoid coil 61 causes a back leak of fuel, and the pressure reduction operation of the common rail 23 is performed. The back leak between the timing of injection of a certain fuel and the timing of the next injection is not necessarily required to be one, but may be performed a plurality of times as necessary.

In the above-described operation of the air strike, the electronic control unit 30 detects the pressure of the common rail 23 by the pressure sensor 31 and the solenoid of the injector 26 by the electronic control unit 30 in response to the detection of the pressure. This is performed by controlling the excitation of the coil 61.

By arbitrarily performing such a back leak, the pressure in the common rail 23 can be reduced as required. For example, the fuel injection pressure according to the engine condition as shown in FIG. It is possible to get it quickly. This allows the state of fuel injection to be promptly adapted to the required combustion.

The fuel injection device according to the present embodiment
Utilizing the back leak in the non-injection region of the injector 26, the common rail 23 after the engine is stopped
To release the residual pressure of the vehicle, thereby ensuring safety during vehicle maintenance.

As shown in FIG. 7A, normal fuel injection is performed by the injector 26 while the key switch is ON. On the other hand, when the key switch is turned off, the signal is input to the electronic control device 30 shown in FIG.
Little by little O the solenoid coil 61 at a time interval where the fuel injection is not carried out a period shorter than the time T ₁
N.OFF is performed so that the injector 26 performs a back leak.

Due to this back leak, the fuel in the common rail 23 is supplied to the fuel passage 62, orifice 54, hydraulic cylinder 51, orifice 52, fuel passage 65, port 6
6, the pressure in the common rail 23 is reduced. Then, after a predetermined back leak is performed, the power supply voltage is switched off. That is, the power supply voltage is cut off with a time lag when the key switch is turned off.

As described above, in the fuel injection device according to the present embodiment, when the key switch is turned off, the electronic control unit 3
A value of 0 causes the injector 26 to perform a back leak operation, whereby the pressure in the common rail 23 is gradually reduced. Therefore, after the engine is stopped, there is almost no residual pressure in the common rail 23, so that safety during maintenance is achieved.

[0047]

According to a first aspect of the present invention, there is provided means for repeatedly switching the solenoid valve of the injector in a cycle shorter than a period during which fuel is injected in response to an engine stop signal.

Accordingly, it is possible to release the residual pressure of the pressure accumulating means by utilizing the back leak of the injector without injecting fuel when the engine is stopped. Safety will be achieved.

According to a second aspect of the present invention, there is provided means for performing a switching operation of the solenoid valve of the injector at a period shorter than a period during which fuel is injected during the timing of fuel injection.

Therefore, the pressure of the pressure accumulating means can be reduced by such switching operation of the solenoid valve, and in particular, the response of the pressure accumulating means to the pressure reduction can be improved. As a result, the fuel pressure accumulated by the accumulator can be set arbitrarily.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a pressure accumulating fuel injection device.

FIG. 2 is a longitudinal sectional view showing the operation of the injector.

FIG. 3 is a longitudinal sectional view showing a specific configuration of an injector.

FIG. 4 is a graph showing a relationship between an engine speed and an output torque.

FIG. 5 is a graph showing a relationship between an injection valve ON time of an injector and an injection amount.

FIG. 6 is a graph showing a pressure reduction operation of a common rail due to a back leak.

FIG. 7 is a graph showing a pressure reduction operation of a common rail when the engine is stopped.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 pressure pump 11 plunger 12 cam 13 pressure chamber 15 tank 16 segmenter 17 filter 18 feed pump 19 fuel filter 20 one-way valve 22 one-way valve 23 common rail (accumulation chamber) 24 one-way valve (pressure limiter) 25 flow limiter 26 Injector 30 Electronic control unit (computer) 31 Pressure sensor 32 Pump control valve 33 Electromagnetic coil 35 Accelerator sensor 36 Engine rotation sensor 37 Cylinder discrimination sensor (engine) 38 Cylinder discrimination sensor (pump) 40 Nozzle body 41 Nozzle needle 42 Valve seat 43 Injection port 44 Fuel reservoir 45 Fuel passage 48 Push rod 49 Press spring 50 Piston 51 Hydraulic cylinder 52 Orifice 53 Small hole 54 Orifice 59 Solenoid valve 60 Compression coil spring 61 Renoidokoiru 62 fuel passage 65 fuel passage 66 ports

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 47/02 F02M 47/02

Claims (2)

[Claims] 1. A fuel injection device in which fuel pressure accumulated by an accumulator is applied to an injector having an electromagnetic valve, and fuel is injected by switching the electromagnetic valve. A fuel injection device, further comprising means for repeatedly switching a solenoid valve of the injector at a cycle shorter than a period during which fuel is injected. 2. A fuel injection device according to claim 1, wherein the fuel pressure accumulated by the pressure accumulating means is applied to an injector having an electromagnetic valve, and fuel is injected by switching the electromagnetic valve. Means for switching the solenoid valve of the injector at a cycle shorter than a period during which fuel is injected.